Study On Measures And Mechanism Of Alkali Activated Aggregate Restraining Alkali-silica Reaction

Alkali-aggregate reaction(AAR)is one of the important reason for leading to the decrease in durability and safety of the concrete structure,since the first case of AAR damage was been found in 1940,a lot of concretes project which had been subjected to AAR damage have been found in the world.There are two types of AAR,the more common one is alkali-silica reaction(ASR),so studying the inhibition measures of ASR is an important content for studying the durability of concrete.At present,using admixture such as fly ash is the most commonly used method for inhibiting ASR at home and abroad,and the study for the inhibitory of ASR by grinding aggregate alkali activity is less,so the effectiveness and inhibition mechanism of inhibiting ASR by admixture needs further research.This paper uses flint as aggregate,which is the typical aggregate alkali activity,mixed with thin flint grinding powder,slag,fly ash,silica fume.First of all,through the rapid mortar bar method to study and compare the effectiveness inhibiting ASR by different content and fineness of the four kinds of admixture.Secondly,using X ray diffractometer(XRD)and scanning electron microscopy(SEM)and energy spectrum(EDS)and,micro analysis was carried out on the sample,for studying and comparing the four types of admixture inhibition mechanism of inhibiting ASR.Finally,by the experiment of quartz glass powder inhibiting ASR researching the applicability of using grinding fine aggregate alkali activity as admixture to inhibit ASR.Test results show that:Flint powder ground has a role in inhibiting ASR,mixed with a certain amount of flint powder can inhibit the destruction of ASR effectively,and increasing the amount or improving the fineness of the flint powder within a certain scope can advance the inhibition effect of ASR.In order to suppress ASR damage effectively,when the fineness of flint powder is 394.2m2/Kg,the amount of mixture should be to reach to 40%;when the flint powder fineness of 701.2m2/Kg,its content should be to reach to 30%.If the fineness of flint powder reaches 899.9m2/kg,the amount of mixture reaches to 20%.The inhibition mechanism on the the destruction of ASR by flint powder mainly reflected in the following aspects: That the secondary volcano ash reaction with Ca(OH)2 was happened not only consumes a large amount of Ca(OH)2 and produce a lot of C-S-H gel with low calcium silicon and stronger alkali capacity.Consuming the alkali,reducing the production of alkali-silica gel.Physical filling effect and the reactant of the secondary volcano ash reaction filling effect make the densification of paste structure,hinder the spreading of ion such as K+,Na+ to reactive aggregate.Quartz glass powder ground also has a role in inhibiting ASR,mixed with a certain amount of quartz glass powder can inhibit the destruction of ASR effectively too.